This specification describes interferometric surface profilers used to generate 3D topography maps of measured surfaces with overlaid color texture information.
Interferometric optical techniques are widely used to measure optical thickness, surface shape (or topography), and other geometric and refractive index properties of precision optical components such as glass substrates used in lithographic photomasks, optical lenses, air bearing surfaces of magnetic head sliders, etc.
For example, one can use an interferometer to combine a test beam reflected from a test surface with a reference beam reflected from a reference surface to form an optical interference pattern (also referred to as a fringe pattern). Spatial variations (e.g., dark and bright fringes) in the intensity profile of the optical interference pattern correspond to phase differences between the combined wave fronts of the test and reference beams caused by, for example, variations in the profile of the test surface relative to the reference surface.